臺灣博碩士論文加值系統

本研究中主要以電腦軟體SOLIDCast輔助分析在不同實驗參數下氣孔與縮孔位置，由於本實驗使用之電腦軟體僅能分析縮孔位置，在實驗中觀察梯形消失模型鑄件各種厚度試片之剖面，比較其孔洞位置與分析結果來判斷氣孔位置。實驗條件分為方案一及方案二常壓下在澆鑄溫度740℃下的模擬結果分析消失模型鑄造之A356鋁合金梯形板狀消失模型鑄件。

對於常壓下鑄造的梯形板狀鑄件在20和25mm鑄件厚度之剖面發現大量分散的孔洞組織，其孔洞位置部分與電腦模擬分析之結果部分相符，在5、10和15mm鑄件厚度之剖面也有少量孔洞，而孔洞分布位置也較靠近鑄件表面，可能為消失模型熱分解之氣體，因冷激層產生而無法由塗層逸散，但電腦模擬並未分析出該位置可能形成缺陷。而高壓下鑄造的梯形板狀鑄件在20和25mm鑄件厚度之剖面在中間位置發現少量集中的孔洞組織，其孔洞位置與電腦模擬分析之結果部分相符，在10和15mm鑄件厚度之剖面僅有微量孔洞，而5mm鑄件厚度之剖面則未觀察到孔洞。

模擬方案中分為兩種方案，這兩種方案分別判斷縮孔，取鑄件各厚度交界觀察其是否有巨觀縮孔之現象，但兩種方案之巨觀縮孔位置大不相同。SOLIDCast模擬的方案中只在20mm及25mm鑄件厚度有產生微縮孔的可能。
在常壓下消失模型鑄件孔洞缺陷平均分佈在各鑄件厚度，而施以高壓厚明顯改善，但縮孔則依然存在。

This study is mainly aimed at the mold flow and solidification computer-aided simulation analyses, which were conducted via the SOLIDCast computer software, on the porosity and shrinkage of A356 aluminum alloy step-type castings. Those castings were made by evaporative pattern casting (EPC). The observations on the porosity at the connection section of various thicknesses of real step-type EPC castings were also compared to the porosity shown on the simulation. The simulation and experimental conditions were classified into two categories, which are separately conducted under normal atmosphere (1 atm) and at the high pressure (10 atm), both with the same casting temperature 740 ℃.

The results of this study reveal that a large amount of porosity dispersed on the connecting section between 20mm and 25mm thicknesses of step-type casting under normal atmosphere. Most of porosity location is similar to that of computer simulation results. There are some porosity on the connecting section among 5, 10 and 15mm casting thicknesses. The reason for the existence of that porosity may be owing to gas products of pattern pyrolysis. But the computer simulation result does not reveal the porosity defects. The connecting section between 20mm and 25mm thicknesses of step-type casting under high pressure atmosphere possess less porosity, which is consistent to the computer simulation result. However trace amount of porosity on the connecting section were existed between 10 and 15mm casting thicknesses. None porosity on the connecting section between 5 and 10mm casting thicknesses was observed. The distribution of porosity is widespread among all connecting sections of casting thicknesses for normal atmosphere, but is improved to be scare under high pressure condition.

There are two programs for computer simulation to understand the shrinkage hole among connecting sections of various casting thicknesses. The Niyama criterion was used to determine the shrinkage location. For SOLIDCast simulation results, only the existence of shrinkage porosity becomes to be possible on the connecting section between 20 and 25mm casting thicknesses. Thus, the prediction on the porosity in the A356 aluminum alloy castings by the SOLIDCast solidification simulation should be unreasonable.

封面內頁
簽名頁
中文摘要............................iii
ABSTRACT...........................v
誌謝................................vii
目錄................................viii
圖目錄..............................x
表目錄..............................xii
符號說明............................xiii

第一章 前言...........................1
第二章 文獻探討.......................3
2.1 A356鋁合金材料特性................3
2.2 鋁合金之凝固模式..................5
2.2.1 凝固收縮現象....................5
2.3 消失模型鑄造法....................6
2.3.1 模型材料.......................6
2.3.2 模型製作過程....................6
2.3.3 模型塗層........................8
2.4 鑄造用電腦軟體之發展與應用..........12
2.4.1 電腦模擬數值分析法...............13
2.5 澆流道系統方案設計.................14
2.6 澆流道系統........................15
2.7 縮孔缺陷..........................16
2.8 高壓凝固..........................18
第三章 實驗方法與步驟...................25
3.1 本研究流程及目的...................25
3.2 鑄件模型繪製.......................25
3.3 SOLIDCast電腦輔助模擬分析..........26
3.3.1圖檔匯入、網格及設定模流參數........26
3.3.2分析結果.........................27
3.4消失模型鑄造流程....................27
第四章 結果與討論......................38
4.1 SOLIDCast模擬分析之結果............38
4.1.1無澆流道之凝固分析結果.............39
4.1.2方案(一)分析結果..................40
4.1.3方案(二)分析結果..................42
4.2實際鑄件孔洞分佈....................42
第五章 結論............................63
參考文獻..............................64

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